The current template target implementation only allows a way to
represent the template position as targeting a single node in the
template AST. However, there is at least one case (banana-in-a-box)
where a given template position refers to two template targets.
This commit expands the contexts that the `TemplateTarget` can return to
include support for the banana-in-a-box syntax, which has two logically
targetted AST nodes given a position within the `keySpan` of the
binding.
PR Close#40185
a893187d51